On extinction. II. The theory of secondary extinction

The formalism developed in the previous paper [Kato, Acta Cryst. (1976), A32, 453-457] is applied to real crystals. If the correlation length of the lattice phase factor is sufficiently smaller than the extinction distance, the ensemble averages of the intensity fields, <I_o> and <I_g>, satisfy a set of energy-transfer equations. Their form is essentially the same as that used in the conventional theory of secondary extinction. However, the physical meanings of the coupling constants connecting <I_o> and <I_g> are different, so that a modification to the theory of secondary extinction is suggested. The conventional model of mosaic blocks is merely a special case and the theoretical framework is free from the model of distorted crystals.